1. Field of the Invention
The present invention relates to a shock protected high stack density suspension system and more particularly to a plurality of such suspension systems which are shock protected during manufacture, during assembly in a head stack assembly, during assembly in a disk stack assembly, and after assembly.
2. Background of the Invention
Suspension systems are employed in magnetic disk drives. A suspension system includes a head/gimbal assembly (HGA) which is connected to an outer end ("suspended" end) of a load beam. The HGA includes a flexure having a window bounded in part by a pair of flexure legs and an outer terminal end portion. Extending inward from the outer terminal end portion is a flexure tongue which is cantilevered into the window. A slider, carrying a magnetic head, is mounted at its top to a bottom of the tongue. A bottom surface of the slider and a pole tip portion of the magnetic head form an air bearing surface (ABS). An inner end of the load beam is connected to an actuator for moving the ABS across a surface of a magnetic disk while a spring force of the load beam preloads the ABS of the slider toward the magnetic disk. When the disk is rotated, the ABS of the slider is supported ("flies") a slight distance from the surface of the disk, in the order of 0.075 um, on a cushion of air (air bearing) which counterbalances the preloading, the air bearing being created by the rotating disk. The actuator then moves the load beam to position one or more sliders at desired concentric tracks on the disks for reading and writing by the magnetic heads. The slider is gimbal supported by the suspension as it flies with respect to the disk.
The connection of the flexure to the load beam is made between a top inner end of the flexure and a bottom of the load beam. A top of the tongue has a load dome that is engaged by the bottom of the load beam at a pivot point. During flight of the slider, slight pitching and rolling movements of the slider are supported by gimballing action of the flexure tongue about the pivot point, the gimballing action in turn being supported by flexure of the legs and terminal end portion of the flexure. In the prior art non-operational roll of the slider is limited by engagement of wings on the flexure with tabs on the load beam.
A high capacity magnetic disk drive employs a plurality of double sided magnetic disks in a disk stack assembly and a plurality of suspension systems in a head stack assembly. The suspension systems, which are supported by an actuator assembly, are interleaved between the disks so that each side of each disk can be read and written by a respective magnetic head. Sliders of top and bottom suspensions in the stack face top and bottom surfaces of top and bottom disks and sliders of each pair of suspension systems between the top and bottom suspensions face opposing surfaces of a respective pair of disks.
Each suspension system is a delicate component before and after its incorporation into a disk drive. The flexure of the HGA is a very thin sheet of metal which can be easily bent under shock loading. At times shock loading may be intense enough to permanently bend the flexure by moving the flexure tongue away from the load beam until its elastic limit has been exceeded. A first improvement is adding roll limiters as taught in the prior art. Once the roll limiters are engaged during a shock event the slider rotates further in pitch. When a flexure tongue is permanently bent, the suspension must be discarded since preloading and gimballing action of the HGA will be unacceptably altered. Unfortunately, intense shock loading can occur during manufacture and even after installation in a disk drive. During manufacture suspensions are transported in trays which can be jostled. After installation the frame supporting the disk drive can be jarred, such as by dropping a laptop computer. Such jarring can cause permanent damage of a suspension which renders a disk drive inoperable.
Various schemes have been proposed to limit the pitch of the HGA. According to one such proposal, the terminal end of a flexure is provided with a pair of tabs that extend over the top of the terminal end of the load beam. As is known, such tabs do not restrict pitch enough to prevent bending of the flexure.
Another pitch limiting scheme is taught in U.S. Pat. No. 5,333,085 wherein a tab is provided on the cantilevered end of the flexure tongue which extends over the top of the load beam through an aperture in the load beam. However, such a tab prevents flexure tongues in a head stack assembly from being compressed by a merge comb when the head stack assembly is installed in the disk stack assembly. A merge comb looks similar to a hair comb; it includes a plurality of fingers which can be interleaved with a column of tongues in a head stack assembly to prevent preloading while maintaining the suspensions in a retracted position until the air bearing surfaces of the sliders assume a parallel relationship. When the air bearing surfaces are parallel each pair of suspensions assumes its lowest height dimension thereby limiting the minimum distance at which disks can be spaced in the disk stack assembly. Accordingly, after assembly of a plurality of suspensions in a head stack assembly the merge comb is placed to merge the suspensions and then the head stack assembly is installed in the disk stack assembly. During installation, the spacing between the air bearing surfaces of the HGAs is very small. If the merge comb cannot obtain a parallel relationship between the sliders then the spacing between disks must be increased in order to permit the head stack assembly to be installed in the disk stack assembly without the sliders engaging and scraping across the surfaces of the disks. Manifestly when the distance between disks in a disk stack assembly increases, disk stacking density is lessened thereby reducing the bit density of the disk drive. In order for a merge comb to perform its intended function, the cantilevered end of a flexure tongue must be adapted for engagement with a finger of the merge comb. This is not practical if the cantilevered end of the flexure tongue has a tab for limiting pitch movement of the flexure. Accordingly, there is a strong felt need for flexure tongues which will limit pitch of flexures and yet cooperate with a merge comb for retracting sliders with their air bearing surfaces parallel with respect to one another.